This invention relates to light-colored, thermoplastic materials and their use in the manufacture of molded articles, especially panels or sheets, having a high weatherability.
It is known to utilize thermoplastic materials, for example, in the form of panels or sheets, for moisture seals. Such panels or sheets can be joined together to form rather large sealing surfaces either by heat welding or by use of solution welding agents such as swelling agents, or special adhesives. Alternatively, they can also be loosely laid on substrates such as concrete, wood, bitumen, and thermal insulating materials containing entrapped air; or they can be glued to such supporting materials at a few selected locations or over their entire surface area with the use of special large-surface area adhesives.
Important characteristics of the panels or sheets produced from the thermoplastic materials include suitable rheological properties, satisfactory weldability, and adequate mechanical properties over a rather wide range of temperatures. In addition, they must also exhibit, above all, a satisfactory resistance to weathering and to other environmental influences. At the high temperatures which can occur, for example, on flat roofs during the height of the summer in Central Europe or in countries having a tropical or subtropical climate, special demands are posed with regard to mechanical characteristics at these elevated temperatures on the one hand, and with respect to weatherability, on the other.
Thermoplastic materials based on carbon-black-containing compounds in most cases are extraordinarily weather-resistant, but, of course, are black. On the other hand, light-colored covering materials, due to their more favorable heat absorption and reflection properties, offer the possibility of keeping bulk temperatures substantially lower than is feasible for black-colored sheets or panels, e.g., by minimizing the effect of increased solar radiation. Also, more attractive optical-architectural effects can be achieved, including the introduction of aesthetically enhancing colors by the addition of colored pigments.
Even in underground construction technology, light-colored panels or sheets offer advantages, e.g., in making repairs, due to the fact that they can be more readily recognized as compared to black-colored panels or sheets.
A prerequisite for the use of such light colored materials is sufficient weatherability; however, this property is substantially poorer in light-colored thermoplastic materials than in black, carbon-containing ones. In most cases, the weatherability is so poor that the practical use of light colored materials is prohibited due to the short lifetime of the sealing sheets produced therefrom.